Show pretty errors when Google Maps API key is empty or invalid

window.alert is overridden with a function that displays the error in
HTML.
If the key is empty, the map code is never loaded.

Also:
Wash the API key for use in HTML.
Handle empty keys (cSettings makes them NULL in the database and "FALSE"
on retrieval).
Factor out window.alert replacement

and turn the element into a P
Use alert replacement on user-facing maps too

Not necessarily pretty, but better than an alert box